The normal boiling point of a certain liquid X is 130.9 °C, but when 19.9 g of urea (NH2) CO are dissolved in 200. g of X, it is found that

Question

The normal boiling point of a certain liquid X is 130.9 °C, but when 19.9 g of urea (NH2) CO are dissolved in 200. g of X, it is found that the solution boils at 134.1 °C instead. Use this information to calculate the molal boiling point elevation constant K, of X. Be sure your answer has the correct number of significant digits x 1 ℃.mol -kg

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MichaelMet 4 years 2021-07-18T23:47:12+00:00 1 Answers 14 views 0

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    2021-07-18T23:48:26+00:00

    Answer:

    K = 1.93 °C/m

    Explanation:

    This question can be solved by formula of elevation of boiling point.

    Boiling T° of solution – Boiling T° of pure solvent = K . m . i

    Our solute is urea.

    Our solvent is X.

    We convert mass of urea to moles: 19.9 g . 1 mol / 60.06g = 0.331 mol

    We convert g of solute to kg = 200 g . 1 kg/ 1000g = 0.2kg

    m = molality → moles of solute / kg of solvent

    m = 0.331 mol / 0.2 kg = 1.66 m

    As urea is an organic compound, no ions will be formed.

    i = 1 (a non ionizing compound)

    Let’s replace data in formula:

    134,1°C – 130.9°C = K . 1.66 m . 1

    3.2 °C / 1.66 m = K

    K = 1.93 °C/m

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